[llvm-commits] [llvm] r112270 - in /llvm/trunk: lib/Analysis/LazyValueInfo.cpp lib/Transforms/Scalar/JumpThreading.cpp test/Transforms/JumpThreading/basic.ll test/Transforms/JumpThreading/lvi-load.ll
Owen Anderson
resistor at mac.com
Fri Aug 27 10:12:30 PDT 2010
Author: resistor
Date: Fri Aug 27 12:12:29 2010
New Revision: 112270
URL: http://llvm.org/viewvc/llvm-project?rev=112270&view=rev
Log:
Use LVI to eliminate conditional branches where we've tested a related condition previously. Update tests for this change.
This fixes PR5652.
Modified:
llvm/trunk/lib/Analysis/LazyValueInfo.cpp
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
llvm/trunk/test/Transforms/JumpThreading/basic.ll
llvm/trunk/test/Transforms/JumpThreading/lvi-load.ll
Modified: llvm/trunk/lib/Analysis/LazyValueInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/LazyValueInfo.cpp?rev=112270&r1=112269&r2=112270&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/LazyValueInfo.cpp (original)
+++ llvm/trunk/lib/Analysis/LazyValueInfo.cpp Fri Aug 27 12:12:29 2010
@@ -656,7 +656,8 @@
// Figure out the possible values of the query BEFORE this branch.
LVILatticeVal InBlock = getBlockValue(BBFrom);
- if (!InBlock.isConstantRange()) return InBlock;
+ if (!InBlock.isConstantRange())
+ return LVILatticeVal::getRange(TrueValues);
// Find all potential values that satisfy both the input and output
// conditions.
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=112270&r1=112269&r2=112270&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Fri Aug 27 12:12:29 2010
@@ -669,6 +669,45 @@
}
}
}
+
+ // For a comparison where the LHS is outside this block, it's possible
+ // that we've branch on it before. Used LVI to see if we can simplify
+ // the branch based on that.
+ BranchInst *CondBr = dyn_cast<BranchInst>(BB->getTerminator());
+ Constant *CondConst = dyn_cast<Constant>(CondCmp->getOperand(1));
+ if (LVI && CondBr && CondConst && CondBr->isConditional() &&
+ (!isa<Instruction>(CondCmp->getOperand(0)) ||
+ cast<Instruction>(CondCmp->getOperand(0))->getParent() != BB)) {
+ // For predecessor edge, determine if the comparison is true or false
+ // on that edge. If they're all true or all false, we can simplify the
+ // branch.
+ // FIXME: We could handle mixed true/false by duplicating code.
+ unsigned Trues = 0, Falses = 0, predcount = 0;
+ for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);PI != PE; ++PI){
+ ++predcount;
+ LazyValueInfo::Tristate Ret =
+ LVI->getPredicateOnEdge(CondCmp->getPredicate(),
+ CondCmp->getOperand(0), CondConst, *PI, BB);
+ if (Ret == LazyValueInfo::True)
+ ++Trues;
+ else if (Ret == LazyValueInfo::False)
+ ++Falses;
+ }
+
+ // If we can determine the branch direction statically, converted
+ // the conditional branch to an unconditional one.
+ if (Trues && Trues == predcount) {
+ RemovePredecessorAndSimplify(CondBr->getSuccessor(1), BB, TD);
+ BranchInst::Create(CondBr->getSuccessor(0), CondBr);
+ CondBr->eraseFromParent();
+ return true;
+ } else if (Falses && Falses == predcount) {
+ RemovePredecessorAndSimplify(CondBr->getSuccessor(0), BB, TD);
+ BranchInst::Create(CondBr->getSuccessor(1), CondBr);
+ CondBr->eraseFromParent();
+ return true;
+ }
+ }
}
// Check for some cases that are worth simplifying. Right now we want to look
Modified: llvm/trunk/test/Transforms/JumpThreading/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/JumpThreading/basic.ll?rev=112270&r1=112269&r2=112270&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/JumpThreading/basic.ll (original)
+++ llvm/trunk/test/Transforms/JumpThreading/basic.ll Fri Aug 27 12:12:29 2010
@@ -147,11 +147,17 @@
; CHECK: @test6
%tmp455 = icmp eq i32 %A, 42
br i1 %tmp455, label %BB1, label %BB2
-
-BB2:
+
+; CHECK: call i32 @f2()
+; CHECK-NEXT: ret i32 3
+
; CHECK: call i32 @f1()
-; CHECK-NEXT: call void @f3()
-; CHECK-NEXT: ret i32 4
+; CHECK-NOT: br
+; CHECK: call void @f3()
+; CHECK-NOT: br
+; CHECK: ret i32 4
+
+BB2:
call i32 @f1()
br label %BB1
Modified: llvm/trunk/test/Transforms/JumpThreading/lvi-load.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/JumpThreading/lvi-load.ll?rev=112270&r1=112269&r2=112270&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/JumpThreading/lvi-load.ll (original)
+++ llvm/trunk/test/Transforms/JumpThreading/lvi-load.ll Fri Aug 27 12:12:29 2010
@@ -1,4 +1,4 @@
-; RUN: opt -S -jump-threading -enable-jump-threading-lvi < %s | FileCheck %s
+; RUN: opt -S -jump-threading -enable-jump-threading-lvi -dce < %s | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.4"
@@ -25,6 +25,7 @@
%toBoolnot.i.i = icmp ult i8 %1, 21 ; <i1> [#uses=1]
br i1 %toBoolnot.i.i, label %bb6.i.i, label %_ZN4llvm8dyn_castINS_11InstructionEPNS_5ValueEEENS_10cast_rettyIT_T0_E8ret_typeERKS6_.exit
+; CHECK-NOT: assert
bb6.i.i: ; preds = %bb.i
tail call void @__assert_rtn(i8* getelementptr inbounds ([5 x i8]* @_ZZN4llvm4castINS_11InstructionEPNS_5ValueEEENS_10cast_rettyIT_T0_E8ret_typeERKS6_E8__func__, i64 0, i64 0), i8* getelementptr inbounds ([31 x i8]* @.str, i64 0, i64 0), i32 202, i8* getelementptr inbounds ([59 x i8]* @.str1, i64 0, i64 0)) noreturn
unreachable
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